Kenneth Grange at home in Hampstead, north London. Photograph: Suki Dhanda for the Observer

At his elegant home in Hampstead in north London – golden parquet floors, Eames lounge chair and ottoman, covetable rosewood sideboard by English designer Robert Heritage – Kenneth Grange, sleek in his black T-shirt, describes to me his latest work: the creation of a chair for the elderly for British manufacturer Hitch Mylius. "It's my first chair," he says, with almost boyish enthusiasm. (He is, though you'd never know it, 82.) "What's interesting is that it's almost a contradiction in modern furniture terms to attempt to make something that is overtly comfortable." He nods in the direction of the aforementioned Eames. "I mean, that's an absolute icon. But it's not comfortable, is it? You need a cushion. Modern furniture is almost always too low and getting off it is a bugger. It's really only designed to make the space look brilliant." Is his own chair comfortable? "Yes, it's bloody comfortable!"

Once you know who Kenneth Grange is – once you've learned a little about his remarkable 50-year career and your eye is in – you see his work everywhere: on streets and stations, in your kitchen, your cupboards and your desk drawer. If the tube had let me down this morning, I might even have travelled here in one of his designs (the London taxi cab, which he remodelled in 1997). Such visual omnipotence, though, is starkly at odds with his personality, which is not grand at all. Grange, modest to a fault, is apt to attribute even his greatest hits – the InterCity 125 train, for instance, which was introduced in 1976 and which is still going strong – to hard work and serendipity rather than his own genius.

The retrospective of his career that is shortly to be staged at the Design Museum is certainly pleasing, but he hopes, too, that it won't cause people to think that he is no longer working. "Because I am – surprise, surprise. Why would I stop? I mean, if a bloke can play the piano, you don't stop him playing it, do you?" It's his wife the unstoppable Grange feels sorry for. "It's a bugger living with a designer, you know. We keep sticking our noses in. She can't buy a tea towel without me having an opinion."

Grange, founding partner of renowned international design consultancy Pentagram, and visiting professor at the Royal College of Art, grew up in London's East End. His father was a policeman, his mother worked in a factory. The family home was, he says, "a good old-fashioned house, a bacon and eggs kind of house": plenty of brown, a three-piece suite, flowery curtains. "And I was rather a compliant little boy, too, so it was very much against character for me to put up my hand when they asked at school if anybody wanted to try for a scholarship to art school."

Once there, though – he enrolled at Willesden School of Art at the age of 14 – life was made simple by the fact that one could either study fine art or commercial art, end of story. "I chose commercial art; we were taught to do things like hand-drawn lettering. Design, though, was not a word we knew." So how did he get interested? Who informed his taste? "Well, I got lucky," he says. "I did my national service – I worked as a technical illustrator – and then I did a series of jobs working as an assistant to architects. And all my taste, all my ideology, came from them."

It was an exciting period to be young and a designer. Postwar Britain might have been austere, but it was optimistic, too. Things needed to be rebuilt and rethought. "It was a buoyant time, and that's the truth," says Grange. "The manufacturers had come back from the war to rebuild their firms and they needed help to do this. So the Council of Industrial Design [now the Design Council] was established by the Labour government as a kind of broking service. Manufacturers would come to them and the council would supply them with the names of designers. The council was very classy, it was run by people of substance. The top echelons were all servicemen. They'd had a tough time, they knew all about loyalties and ethics and they were scrupulously fair. But I also think I was probably the cheapest and quickest designer on their list."

The first commission he landed via this route (in 1958) was a parking meter for Venner. "I took [the project] on my honeymoon. It was the very first parking meter in Britain. Westminster Council had gone to America and contracted a company there to produce its meters, but when they showed them to the council, which had to approve all street furniture, they didn't like it. So they were stuck! They needed me to make it look pretty."

Soon after, he landed two rather heftier clients. First, there was Kenwood, for whom he restyled the Kenwood Chef in just three days. Then there was Kodak. "I couldn't yet make a living from product design, so I was working doing the displays for the Kodak pavilion at the World Trade Fair. I was arranging the products on the stand and someone overheard me say, 'It's a shame these are so ugly; I could make this really good if they weren't.' The next day, the phone rang. It was the head of development at Kodak, and he said, 'I understand you're going to design a camera for us.' It was thrilling, but I was scared, too, because I didn't know cameras. But again, there was an element of luck involved. I just happened to be in the right place at the moment when Kodak decided to start selling cameras for profit. Up until this point, their cameras were sold at a loss in order to shift film."

The Kodak Instamatic 33 film camera designed by Kenneth Grange in 1968. Photograph: Alamy

In 1959, Grange designed the Kodak 44A, in 1968, the Instamatic, and in 1972 the Pocket Instamatic, the first in a new generation of portable cameras. These were good years. He drove an E-Type Jaguar, and hung out on the King's Road.

His subsequent successes included irons for Morphy Richards, pens for Parker, the Adshel bus shelters of 1993, the "rural post box" for the Royal Mail in 1996… the list is long and varied. It is, however, the InterCity 125 of which he remains most proud. "Because it's big, and I use it almost weekly, to come up from my place in Devon," he says. "I was only supposed to redesign the paintwork. But, for my amusement, I decided to have a go at the shape, too. I did work on the aerodynamics, testing it in wind tunnels with the help of an engineer I was employing. I showed it to them with some trepidation. It was a bloody nerve, to be honest. If I'd been on the British Rail board, I'd have told me to piss off. But they weren't difficult to persuade in the end because the argument was sound: the design made the train more efficient."

So what about design in Britain in 2011? Are things more or less beautiful-looking? "Well, there's a lot of it [design] about, to be honest, and it's utterly disposable, most of it. You can go to a factory in China where they make toasters for every company you can possibly think of, and they will show you 20 new designs you can take away that morning, and you will leave with four for your own company, and you will return in a year for another four. It's an awful thing to say, but the poorer we are [as a nation], the more chance there is of us being more disciplined about what we buy.

"I'd like people to pay much more and keep things for ever. These things [he points to my digital tape recorder] are little miracles and it's a travesty of morality to throw them away. It offends me. As for the look of things, well, Apple is enjoying a reputation as the maker of the sleekest things. But they're a bit up their own arse, to be honest. Their things are overdesigned. I've got a Mac mini upstairs and every morning I try and fail to find the button on the back."

Is there anything Grange wishes he had designed? What makes him envious? "Well, the Scandinavians still take some beating. I've got a lamp called the Artichoke [by Poul Henningsen] and it's bloody brilliant." As for a piece of design he would like to own, he "wouldn't mind" an Aston Martin.

"Probably one of the later ones. They're as good a piece of motor styling as you can get, a piece of sculpture, really. That's why the place for them is indoors. It's amusing to go fast, but it's not important. The look is the thing. Actually, I used to know a wonderful, cranky pair of artists and they had a Morris Minor they loved and it was in their living room." Really? He laughs. "Yes, really. They had to take the house apart to get it in, but that's where they kept it, I promise you."

Kenneth Grange: Making Britain Modern is at the Design Museum, London SE1